A gold digger is an informal term for:
A woman who associates with or marries a man chiefly for material gain
What would the gold digger's man be called? A mark? A sugar daddy?
Edit: I'm editing after my sugar daddy term has been reposted a couple of times, strangely with great success.
I'd like a term for a man being targeted by the gold digger. So obviously as I listed sugar daddy in the question I felt that it was unsatisfactory; for example it works poorly here:
He's her sugar daddy.
While this is very accurate for a gold digger's man. You cannot take from this that he's being targeted, it even sounds like he's doing the targeting. This is closer:
He's her mark.
It's clear that he is being targeted. But unless the gold digger is also an assassin it seems a bit unclear what he's being targeted for.